1. Field of the Invention
The invention generally relates to pumps and to condition responsive control of a pump drive motor. The invention also generally relates to hydrotherapy spas and swimming pools, with a condition responsive means for agitating or circulating water in the pool. The invention also generally relates to electrical communications and to a condition responsive indicating system. More specifically, the invention relates to detection of an underload condition in a swimming pool circulation pump motor and a responsive shutdown of the pump motor.
2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98
Swimming pools and other aquatic facilities require a circulation system to remove water, filter the water, optionally heat the water, and return the processed water to the facility. A circulation pump draws water from the facility under vacuum, also called “negative pressure,” and pumps the water under positive pressure back to the facility. The circulation pump is powerful and produces considerable negative pressure at the connection of any of various pump intake pipes within the pool.
Pools are designed to provide several pump intake points so that the pump can draw from any or all of them. These pump intake points are referred to as suction outlet fittings. If any one suction outlet fitting becomes clogged, the pump draws from the others. In turn, if a bather covers any one of the pump intake points, he should not be held to it by excessive vacuum. Yet, various accidents take place wherein a bather is trapped against a pump intake point by high suction or negative pressure. The possible reasons for this result are many, including poor initial design and construction of the circulation system, or the other intake points may be clogged or simultaneously blocked. Swimming pools should be equipped with a fast-action safety system to release the trapped bather before he might drown or suffer other injury. A safety system of this type is referred to as a Safety Vacuum Release System or, as a shorthand term, SVRS.
Several different types of SVRS are known, each operating in a different manner. The most consistent factor is that they operate by monitoring the vacuum level within the circulation pump intake pipe. A suction entrapment event always is accompanied by an abrupt increase in vacuum level within the circulation pump intake pipe. If the system detects an abrupt increase in vacuum, it actuates a release mechanism. Three general types of release mechanisms are known.
In the first type of release mechanism, the pump can be shut off. Two patents demonstrate that vacuum level can be monitored and used to indicate when a circulation pump should be shut off. U.S. Pat. No. 6,059,536 to Stingl shows an emergency shutdown system in which a vacuum switch is connected to a pump shutoff switch. In case of blockage or a suction entrapment event, the vacuum switch senses the increase in vacuum and triggers the shutoff switch to cut off line current to the circulation pump. As a result, the high vacuum dissipates and releases the bather or other blockage. U.S. Pat. No. 6,342,841 to Stingl shows another emergency shutdown system wherein a microcontroller stores various vacuum profiles for various modes of operation. A comparator within the processor compares real time vacuum data with a stored profile. In case of a detected deviation from the profile, the processor signals the pump, relay to shutdown the circulation pump. Thus, several methods allow an increase in sensed intake vacuum to shut down a circulation pump to allow vacuum level to neutralize.
In a second type of release mechanism, the suction line is vented to atmosphere in order to neutralize the vacuum. U.S. Pat. No. 5,682,624 to Ciochetti shows a valve mounted to a suction line. The valve opens in response to a predetermined high vacuum level in the suction line to vent air into the line, breaking the vacuum and causing the circulation pump to lose prime. U.S. Pat. No. 5,991,939 to Mulvey shows a specific valve in a four-port fixture. Water from the suction inlet pipe flows through two aligned ports. If the suction level becomes higher than a predetermined value, cross-ports open to admit air. U.S. Pat. No. 6,098,654 to Cohen shows another specific valve that is installed in a suction line. The valve opens to admit atmosphere in response to predetermined high vacuum level, and a spring ensures that the valve fully opens for rapid action. Venting the circulation system is effective but carries certain drawbacks. Among them, the pump loses prime, which increases the difficulty in restarting the system. Another drawback is that the pump may run dry, which can damage the pump.
In a third type of release mechanism, a device monitors vacuum in the suction line and responds to the detection of a high vacuum level by reversing the direction of water flow in the suction line. United States published patent application 20030106147 to Cohen et al. shows a system for converting high vacuum level into a positive reverse pressure. The direction of water flow is reversed, thus propelling the victim away from the suction outlet fitting by positive force. This type of system offers a high degree of safety but has the drawback of requiring considerable extra equipment and corresponding room to house such equipment.
A problem exists in the retrofit market for updating older circulation systems with SVRS technology. Known SVRS systems require the addition of significant new equipment to an existing circulation system. Often there is not room for the additions within existing housings, which then requires expensive updating.
It would be desirable to have an effective SVRS system that requires substantially no additions in order to retrofit a circulation system that previously had no SVRS system. Similarly, it would be desirable to have an effective retrofit SVRS system that fits within the existing housing of a system not designed to receive a SVRS.
Circulation systems are present in substantially all aquatic facilities. Such systems are necessary for filtration, sanitization, heating, hydrotherapy, and the operation of water features such as decorative fountains. A circulation pump provides the water flow within these circulation systems. An electric motor is connected to the pump to provide motive power. The invention provides a new method of sensing and responding to blockage or bather entrapment. The new method adapts a motor with supplemental or integral load-sensing capability to sense when the suction intake line is blocked.
Load-sensing systems monitor the operation of an electric motor and determine the power level that the motor is producing. These systems detect overload and underload conditions. Such systems can shut off the motor in response to sensing an undesirable overload or underload condition. The intended purpose of these systems is to protect against damage to the motor or to an associated, powered machine or the product being produced by the machine. Such systems also can prevent waste of electrical power. The following patents illustrate this type of load-sensing system.
U.S. Pat. No. 4,123,792 to Gephart et al. shows a load sensing system that monitors an electronic signal proportional to the mechanical power output of the motor. This signal is detected by rectifying a signal that is an analog of motor current in phase with the motor voltage and time averaging the rectified signal. Comparing the averaged signal to a reference level permits the interruption of motor current for an underload or an overload condition. The circuit permits detection of excessive ice formation on an outdoor heat exchanger of a heat pump system. The circuit is connected to an impeller drive motor that forces air across the heat exchanger. The circuit stops the motor and initiates a de-ice procedure when ice blockage causes mechanical power delivered by the motor to deviate to a selected level.
U.S. Pat. No. 4,419,625 to Bejot et al. shows a device that determines the mean power absorbed from a current supply by measuring the current in a phase and the voltage between two phases, determining the product of the two, and integrating the product. A first potentiometer provides a proportion of the voltage, which is an image of the current, and subtracts it from that voltage between phases. A second potentiometer provides a proportion of the voltage between phases and subtracts if from the product. A third potentiometer provides a proportion of a constant voltage and subtracts it from that product. The third potentiometer is adjusted so that the output power of the integrator is zero when the motor rotates under no-load condition.
U.S. Pat. No. 5,473,497 to Beatty shows a device for measuring energy delivered by a motor to a load. The device is connected to the motor, which is coupled to the load and connected to a power source through first and second power supply lines. The device includes a line voltage sensing circuit for sensing the voltage across the power supply lines, a line current sensing circuit for sensing the current flowing through the motor, and a pulse width modulator that modulates the sensed voltage to produce a pulse width modulated first electrical signal. The device also includes a first switch, responsive to the pulse width modulated first electrical signal, which modulates an output of the line current sensing circuit to produce a power waveform. An integrator integrates the power waveform to produce an output signal indicative of the energy delivered by the motor to the load. The device further includes a switch controller that compares the output signal to a first reference signal to detect the existence of an overload condition. The switch controller compares the output signal to a second reference signal to detect the existence of an underload condition. The switch controller opens a second switch to disconnect the motor from the power source in response to either an overload condition or an underload condition.
U.S. Reissue Pat. RE 33,874 to Miller shows an underload protection system for an electric motor connected to first and second power supply lines, wherein the lines are connectable to an AC power supply. The system provides a line voltage sensing circuit connected to the first power supply line. The sensing circuit has a line voltage signal impressed thereon. An amplitude adjustment circuit is connected to the voltage sensing circuit for adjusting the line voltage signal to produce an amplitude adjusted voltage signal. A line current sensing circuit is connected to the second line and has a line current signal impressed thereon. A phase adjustment circuit is connected to the current sensing circuit for adjusting the phase of the current signal to produce a phase adjusted current signal. A phase responsive circuit is connected to the amplitude adjustment circuit and to the phase adjustment circuit for producing an adjusted power factor signal. A disconnect circuit is connected to the phase responsive circuit for disconnecting the power lines when the power factor is below a preset value.
It would be desirable to employ load-sensing technology as an accurate and responsive technique for determining occurrence of an aquatic suction entrapment event.
To achieve the foregoing and other objects and in accordance with the purpose of the present invention, as embodied and broadly described herein, the method and apparatus of this invention may comprise the following.